An IGBT is a bipolar transistor device that can be used as an electronic switch for switching an electrical load. An IGBT can be implemented with a voltage blocking capability of up to several kilovolts (kV).
An IGBT includes a gate electrode adjacent a body region and dielectrically insulated from the body region by a gate dielectric. The body region of a second doping type separates a first emitter region (source region) of a first doping type from a base region (drift region). The IGBT further includes a second emitter region (drain region) of a second doping type complementary to the first doping type. In an on-state of the IGBT, the gate electrode generates a conducting channel in the body region along the gate dielectric so that the first emitter region injects charge carriers of a first type through the conducting channel into the base region, and the second emitter region injects charge carriers of a second type into the base region. The charge carriers of the first type and the second type form a charge carrier plasma in the base region. This charge carrier plasma results in a relatively low on-resistance of the IGBT. For example, in the on-state the voltage between a first emitter terminal and a second emitter terminal of an IGBT with a voltage blocking capability of about 1200V is only between 1V and 3V.
When the IGBT switches from the on-state to an off-state, the gate electrode interrupts the conducting channel in the body region. This allows an electrical potential of the second emitter region to increase relative to an electrical potential of the first emitter region. However, as the electrical potential of the second emitter region increases, a capacitance (often referred to as feedback capacitance) between the gate electrode and the second emitter region (which corresponds to a capacitance between the gate electrode and the base emitter region) may cause the gate electrode to be charged such that the IGBT again switches on in an undesired way.
There is therefore a need to provide an IGBT with a reduced feedback capacitance.